In recent years, microfiltration is used in wastewater and drinking water treatments, and food and pharmaceutical industries. However, it is well known that one of the principal limitations to the widespread application of the microfiltration process is membrane fouling, which results in a dramatic increase in the filtration resistance accompanying with the progress of filtration, thereby leading to a severe flux decline. Such membrane fouling may be brought about by the clogging of membrane pores and/or the particle deposition on the membrane surface referred to as the filter cake. In the process of using microorganisms, the feed solution is a complex mixture comprising bacterial flocks and microbial metabolite. Therefore, it is essential to clarify the mechanism of flux decline behaviors in microfiltration of microorganism and its metabolite. The key objective of this study is to examine the effect of polysaccharide-protein interaction on membrane fouling caused by microbial metabolite since the microbial metabolite is composed mainly of polysaccharides and proteins...